A. Field Of The Invention
The present invention relates to pivot joints for rotary levers. It is especially suitable for use with engine speed control levers.
B. Description Of The Art
Rotary levers mounted by a pivot joint find many different applications. For example, one common application is a speed control lever mounted on a lawn mower or other power tool. A cable or other suitable means typically connects the lever to the throttle of the engine for the mower so that the mower operator can remotely adjust the mower's speed.
In these types of joints, it is typical to mount the lever so that it rotates about the shank of a connector, which fastens the lever to the mower housing or to other mounting hardware. The prior art has commonly used a rivet or a threaded fastener pair such as a nut and bolt to achieve this connection.
A drawback with prior joints of this general type is that the torque required to pivot the lever has varied greatly from assembly to assembly. Even if the component parts of the joint are within desired specifications, assembly process variables due to dimensional tolerances, hardness tolerances in rivets, and tightening torque tolerances in threaded fastener pairs result in variation of the torque from one assembly to another.
Spring washers such as "belleville" type washers have been applied in certain types of pivot connections, but even in these prior constructions, the force exerted by the spring has varied significantly with process variables. As a result, there has been greater scatter in the lever operating torque from assembly to assembly than desired.